This invention relates to a novel hydrolyzed yam starch composition and the process for making and using the same. More particularly, this invention relates to the discovery that the starch of certain varieties of yams which is hydrolyzed in the presence of insoluble metal salts formed in situ is a surprisingly effective flocculant in destabilizing dilute as well as thick sludge suspensions.
In general, the suspensions destabilized by the starch composition of this invention are aqueous colloidal suspensions containing either clay minerals or metal oxides-hydroxides which are formed in large volume during mining operations in the recovery of such materials as coal, bitumen from tar sands and metals and such suspensions are also formed in paper making operations. In the case of metal mining operations, suspensions known as slimes are formed, typically phosphate slimes or like materials produced in the mining of copper, nickel, and titanium. In coal and tar sands minings, for example, the mining effluent typically contains dilute or thick clay mineral suspensions. In paper making processes cellulosic fines, clays and other solids are present in the large volumes of liquids obtained.
In order to properly dispose of these voluminous mining discharges, regardless of their source, flocculants have conventionally been employed to destabilize these suspensions and thus permit the effective separation of water from solids. The use of wheat, corn and potato starch which has been hydrolyzed in the presence of metal salts formed in situ has been disclosed in U.S. Pat. No. 4,289,540 which issued on Sept. 15, 1981 and is hereby incorporated by reference. It has now been found that surprisingly superior flocculation is obtained if starch from certain specific varieties of yam is used for preparing the hydrolyzed starch composition to give the starch flocculant.